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Effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome: systematic review and meta-analysis

Response to authors of previous rapid responses

Editor

We are grateful for the interest that our recent article concerning
the efficacy of fibre, antispasmodic drugs, and peppermint oil in
irritable bowel syndrome (IBS) has generated, and the important and
exciting debate it has stimulated

We agree with Dr. Dib that IBS is a chronic, relapsing and remitting
condition. We chose a minimum duration of therapy in randomised controlled
trials (RCTs) of the agents we studied in our systematic review and meta-
analysis of 1 week for the reasons we discussed in our article. [1]
However, 34 of the 35 eligible studies randomised patients to therapy in
excess of 1 week. The remaining trial [2] did not have any significant
impact on the overall conclusions when it was excluded from the analysis
(number needed to treat (NNT) with antispasmodics = 6; 95% confidence
interval 4 to 10). The minimum duration of therapy used in the trials of
fibre in IBS that we identified was 4 weeks, and the majority of RCTs used
12 weeks or more.

With regard to Professor Whorwell’s comments, we stated clearly in
the abstract of our article that the beneficial effect of fibre was
limited to ispaghula husk, [1] which is also known as psyllium. We cannot
be held responsible for the misrepresentation of our findings by the
“popular press”.

Dr. Leeds et al. make the important point that antidepressant drugs,
particularly tricyclic antidepressants, were also of benefit in IBS, with
an NNT in our systematic review and meta-analysis of 4. [3] However, there
was also a beneficial effect of a newer class of antidepressants,
serotonin re-uptake inhibitors, in IBS in this meta-analysis. The NNT was
3.5, albeit in a smaller number of RCTs containing fewer patients.

With respect to any role for non-pharmacological therapies in the
management of IBS, we have also examined this issue. We are not aware of
any published RCTs of homeopathy in IBS. There is an existing systematic
review of the efficacy of various psychological therapies in IBS,
conducted by Lackner et al., [4] which identified 10 trials that provided
extractable dichotomous data for pooling. As Drs. Plotnikoff and Weisberg
correctly state the NNT with psychological therapies reported in this
systematic review was 2. While this may appear very appealing,
unfortunately there were only a total of 185 patients included in these
RCTs, and 9 of the 10 trials in this systematic review emanated from a
single centre in the United States, which suggests that the treatment
effect may have been overestimated. In our own systematic review and meta-
analysis of the efficacy of psychological therapies in the management of
IBS, which identified 20 RCTs containing 1278 patients, we reported an NNT
to improve or cure 1 patient’s symptoms of 4. [3] We conducted a
sensitivity analysis that excluded the 9 RCTs conducted by the same group
of investigators, which demonstrated a reduced, though still statistically
significant, treatment effect of psychological therapies on global IBS
symptoms. There were only 2 of these 20 RCTs comparing hypnotherapy to
supportive therapy or waiting list control in 40 patients.

The medical management of IBS remains unsatisfactory, and no single
intervention has been shown to alter the natural history of the condition
convincingly, but data from these recent studies, which were performed to
inform the updated American College of Gastroenterology monograph on the
management of IBS, [5] suggest there are both pharmacological and
psychological therapies that are effective in IBS, at least in the short-
term.